Process for producing impact-resistant polyamide resin compositions

ABSTRACT

An impact-resistant polyamide resin is produced by 
     preparing Mixture (I) by melt-kneading (A) a polyamide resin with (B) at least one modified olefin polymer selected from the group consisting of olefin rubbers having an unsaturated dicarboxylic acid anhydride added thereto, α-olefin polymers having an unsaturated dicarboxylic acid anhydride added thereto, crystalline ethylene-α-olefin copolymers having an unsaturated dicarboxylic acid anhydride added thereto, and ethylene-ethylenic unsaturated ester copolymers having an unsaturated dicarboxylic acid anhydride added thereto, 
     preparing Mixture (II) by melt-kneading Mixture (I) with (C) a polyfunctional compound having in the molecule two or more functional groups reactive with carboxyl group, carboxylic acid anhydride group or amino group, and 
     melt-kneading Mixture (II) with (D) a polyamide resin. 
     The impact-resistant polyamide resin composition obtained by the process of the present invention has an excellent processability and can be made into various molded products, sheets or films by injection molding or extrusion molding. The thus obtained products have good physical properties, in particular, an excellent impact strength.

The present invention relates to a process for producing a polyamideresin composition which can be utilized in the form of molded articles,sheets, films, etc. by means of injection molding, extrusion molding,etc.

More particularly, the present invention relates to a process forproducing a polyamide resin composition having an excellent impactresistance, a good balance in other physical properties and a goodprocessability, which process comprises melt-kneading a polyamide resinwith an olefin polymer modified with an unsaturated dicarboxylic acidanhydride in a specific blending manner.

Polyamide resins have been widely used as engineering plastics becauseof their good stiffness, wear resistance, chemical resistance, heatresistance and electrical properties.

They, however, are poor in impact resistance, molding stability, etc.Such defects are obstacles to opening-up of new avenues of practical usefor them.

Various methods have heretofore been proposed for improving the lowimpact resistance, a defect of polyamide resins.

Typical methods for the improvement are, for example, methods comprisingadding a polymer of modified ethylene copolymer containing active groupsreactive with polyamide resins and having a rubber elasticity, asdisclosed in JP-A-53-146754, JP-B-54-4743, JP-B-5544108, JP-A-58-23850,etc.

However, as a result of examination, the present inventors have foundthat although a molded product having a somewhat improved impactresistance can be obtained according to the above prior art, theimprovement is not sufficient. Furthermore, the molded product was foundto be unsatisfactory from the viewpoint of balance in physicalproperties such as heat resistance, stiffness and impact resistance.

That is, it was found that the somewhat improved impact resistance andflexibility of the molded product are offset by its mechanicalproperties such as stiffness, tensile strength, hardness, heatresistance, etc., which are considerably inferior to those of polyamideresins themselves. Moreover, the above prior art methods aredisadvantageous, for example, in that they often yield a colored moldedproduct having an ugly appearance, whose applications are limited.

Thus, there has not yet been produced any polymer of modified ethylenecopolymer type which is suitable for addition to a polyamide resin anddoes not cause the problems described above, and it has been stronglydesired to develop a polyamide resin composition which has an improvedimpact resistance without deterioration of other physical properties.

The present invention was made in order to improve the low impactresistance, the defect of a polyamide resin while solving the aboveproblems without deterioration of its mechanical properties such as heatresistance and stiffness, by melt-kneading a specific olfein polymermodified with an unsaturated dicarboxylic acid anhydride with thepolyamide resin by a special blending method. An object of thisinvention is to provide a process for producing a polyamide resincomposition comprising a polyamide resin as its main constituent, whichis excellent in impact resistance, mechanical properties such as heatresistance, stiffness and the like, and flow properties.

According to the present invention, there are provided a process forproducing an impact-resistant polyamide resin composition whichcomprises

(1) preparing Mixture (I) by melt-kneading (A) 60 to 20 parts by weightof a polyamide resin with (B) 40 to 80 parts by weight of at least onemodified olefin polymer selected from the group consisting of olefinrubbers having 0.01 to 9% by weight of an unsaturated dicarboxylic acidanhydride added thereto, α-olefin polymers having 0.01 to 9% by weightof an unsaturated dicarboxylic acid anhydride added thereto, crystallineethylene-α-olefin copolymers having 0.01 to 9% by weight of anunsaturated dicarboxylic acid anhydride added thereto, andethylene-ethylenic unsaturated ester copolymers having 0.01 to 9% byweight of an unsaturated dicarboxylic acid anhydride added thereto,

(2) preparing Mixture (II) by melt-kneading 100 parts by weight ofMixture (I) with (C) 0.01 to 20 parts by weight of a polyfunctionalcompound having in the molecule two or more functional groups reactivewith carboxyl group, carboxylic acid anhydride group or amino group, and

(3) melt-kneading 100 parts by weight of Mixture (II) with (D) 50 to1,000 parts by weight of a polyamide resin; and

a process for producing an impact-resistant polyamide resin compositionwhich comprises

(1) preparing Mixture (I) by melt-kneading (A) 60 to 20 parts by weightof a polyamide resin with (B) 40 to 80 parts by weight of a modifiedolefin polymer obtained by melt-kneading 100 parts by weight of at leastone olefin polymer having a glass transition temperature of -10° C. orlower selected from the group consisting of olefin rubbers, α-olefinpolymers, crystalline ethylene-α-olefin copolymers and ethyleneethylenicunsaturated ester copolymers, with 0.1 to 10 parts by weight of anunsaturated dicarboxylic acid anhydride,

(2) preparing Mixture (II) by melt-kneading 100 parts by weight ofMixture (I) with (C) 0.01 to 20 parts by weight of a polyfunctionalcompound having in the molecule two or more functional groups reactivewith carboxyl group, carboxylic acid anhydride group or amino group, and

(3) melt-kneading 100 parts by weight of Mixture (II) with (D) 50 to1,000 parts by weight of a polyamide resin.

The polyamide resins as components (A) and (D) in this invention arehigh molecular weight polymers in which amide linkages (CONH) occuralong the molecular chain obtained, for example, by ring openingpolymerization of a lactam of a ring having not less than three carbonatoms, polymerization of an ω-amino acid, or polycondensation of adibasic acid and a diamine.

Specific examples of the polyamide resins are homopolymers ofε-caprolactam, aminocaproic acid, enantholactam, 7-aminoheptanoic acid,11-aminoundecanoic acid, etc.; polymers obtained by polycondensation ofa diamine such as butanediamine, hexamethylenediamine,nonamethylenediamine, undecamethylenediamine, dodecamethylenediamine,methaxylenediamine or the like and a dicarboxylic acid such asterephthalic acid, isophthalic acid, adipic acid, sebacic acid, dodecanedibasic acid, glutaric acid or the like; and copolymers of the abovemonomers.

More specific examples of the polyamide resins are aliphatic polyamideresins such as polyamide 46, polyamide 6 (poly-ε-caprolactam), polyamide66 (polyhexamethylene adipamide), polyamide 610 (polyhexamethylenesebacamide), polyamide 11 (poly-11-aminoundecanoic acid), polyamide 12(polylauric lactam), polyamide 612 (polyhexamethylene dodecanoamide),etc., and aromatic polyamide resins such aspolyhexamethylenediamineterephthalamide,polyhexamethyleneisophthalamide, xylenegroup-containing polyamides, etc.

Of these, polyamide 6, polyamide 66 and polyamide 12 are particularlypreferable.

In addition, various copolymer Nylon resins having a melting point of80° to 200° C. which are commercially available as resins for hot-meltadhesives and the like, can also be used alone or in combination withpolyamides having a melting point of 200° C. or higher.

In the present invention, the polyamide resins as components (A) and (B)may be the same or different.

The olefin polymer modified with an unsaturated dicarboxylic acidanhydride used in the component (B) of this invention is at least onemodified olefin polymer selected from the group consisting of olefinrubbers having 0.01 to 9% by weight of an unsaturated dicarboxylic acidanhydride added thereto, α-olefin polymers having 0.01 to 9% by weightof an unsaturated dicarboxylic acid anhydride added thereto, crystallineethylene-α-olefin copolymers having 0.01 to 9% by weight of anunsaturated dicarboxylic acid anhydride added thereto, andethylene-ethylenic unsaturated ester copolymers having 0.01 to 9% byweight of an unsaturated dicarboxylic acid anhydride added thereto. Theamount of unsaturated dicarboxylic acid anhydride added is preferably0.1 to 2% by weight, more preferably 0.3 to 1.6% by weight.

The olefin polymer modified with an unsaturated dicarboxylic acidanhydride can be produced by meltkneading 100 parts by weight of atleast one olefin polymer having a glass transition temperature of -10°C. or lower selected from the group consisting of olefin rubbers,α-olefin polymers, crystalline ethyleneαolefin copolymers andethylene-ethylenic unsaturated ester copolymers, with 0.1 to 10 parts byweight of an unsaturated dicarboxylic acid anhydride. The blendingamount of the unsaturated dicarboxylic acid anhydride is preferably 0.5to 5 parts by weight, more preferably 1 to 2 parts by weight.

Specific examples of the olefin rubber are rubbers comprising acopolymer of ethylene and an αolefin having 3 or more carbon atoms. Morespecific examples thereof are copolymers of ethylene and propylene,butene-1, hexene-1, 4-methylbutene-1, 4methylpentene-1 or the like. Ofthese, copolymer rubber of ethylene and propylene is particularlypreferable. These ethylene copolymer rubbers may be terpolymers furthercomprising a nonconjugated diene such as methylenenorbornene,ethylidenenorbornene, 1,4-hexadiene, dicylopentadiene, etc. in additionto ethylene and an α-olefin having 3 or more carbon atoms. There can befurther exemplified butyl rubbers, ethylene-acrylic ester copolymerrubbers, etc.

Specific examples of the α-olefin polymer and the crystallineethylene-α-olefin copolymer are polyisobutylenes, crystallinepropylene-ethylene copolymers and crystalline ethylene-butylenecopolymers.

Specific examples of the ethylene-ethylenic unsaturated ester copolymerare ethylene-α,β-unsaturated carboxylic acid alkyl ester copolymers,ethylenecarboxylic acid vinyl ester copolymers, ethylene-α,βunsaturatedcarboxylic acid alkyl ester-carboxylic acid vinyl ester terpolymers.More specific examples thereof are copolymers of ethylene and at leastone monomers selected from the group consisting of methyl acrylate,methyl methacrylate, ethyl acrylate, ethyl methacrylate and vinylacetate. Of these, ethylene-methyl methacrylate copolymers andethylene-vinyl acetate copolymers are preferable.

The olefin polymer used in the present invention is an olefin polymerhaving a glass transition temperature of -10° C. or lower. When theglass transition temperature is higher than -10° C., the improvement inimpact resistance of the resulting polyamide resin composition is notsufficient in some cases.

The unsaturated carboxylic acid anhydride includes, for example, maleicanhydride, itaconic anhydride, citraconic anhydride,bicyclo[2,2,1]hepta-5ene-2,3-dicarboxylic acid anhydride (himic acidanhydride), tetrahydrophthalic anhydride,bicyclo[2,2,2]octa-5ene-2,2-dicarboxylic acid anhydride,4-methylcyclohexa4-ene-1,2-dicarboxylic acid anhydride,1,2,3,4,5,8,9,10octahydronaphthalene-2,3-dicarboxylic acid anhydride,and 7-oxabicyclo[2,2,1]hepta-5-ene-2,3-dicarboxylic acid anhydride. Ofthese, maleic anhydride is particularly preferable.

The olefin polymer modified with an unsaturated dicarboxylic acid inthis invention is produced by melt-kneading 100 parts by weight of anolefin polymer with 0.1 to 10 parts by weight of an unsaturateddicarboxylic acid anhydride. When the amount used of the unsaturateddicarboxylic acid anhydride is less than 0.1 part by weight, theimprovement in impact resistance of the resulting polyamide resincomposition is not sufficient. When it exceeds 10 parts by weight, theamount of a gel formed is disadvantageously increased.

In melt-kneading the unsaturated dicarboxylic acid anhydride, it ispreferable to add a free-radical initiator which generates a radicaleffectively at the melt-kneading temperature. Specific examples of thefree-radical initiator are organic peroxides such as1,3-bis(t-butylperoxyisopropyl)benzene,1,1-bis(tbutylperoxy)-3,3,5-trimethylcyclohexane, t-butyl peroxylaurate,dicumyl peroxide and benzoyl peroxide. When a free-radical initiator isused, the amount used is preferably 0.01 to 5 parts by weight, morepreferably 0.02 to 2 parts by weight, most preferably 0.08 to 1 part byweight, per 100 parts by weight of the olefin polymer.

In melt-kneading the unsaturated dicarboxylic acid anhydride, anaromatic vinyl monomer such as styrene may be added in an amount of 0.1to 5 parts by weight, preferably 0.2 to 3 parts by weight, morepreferably 0.5 to 1 part by weight, per part by weight of theunsaturated dicarboxylic acid anhydride (these amounts correspond to0.01 to 50 parts by weight, 0.02 to 30 parts by weight and 0.05 to 10parts by weight, respectively, per 100 parts by weight of the olefinpolymer). The addition of an aromatic monomer permits reduction of theamount of a gel generated and increase of the amount of the unsaturateddicarboxylic acid anhydride added to the olefin polymer, and hence isvery preferable for conducting the present invention.

The temperature at which the olefin polymer and the unsaturateddicarboxylic acid anhydride are melt-kneaded together is not critical.It is preferably 180° to 300° C. Although a kneading machine for themelt-kneading is not critical, an extruder is usually preferred becauseit permits continuous production.

The component (C) used in this invention, i.e., the polyfunctionalcompound containing in the molecule two or more functional groupsreactive with carboxyl group, carboxylic acid anhydride group or aminogroup, is not critical so long as it is a compound having intermolecularcrosslinking reactivity with the modified olefin polymer (B) or thepolyamide resin (A).

As the polyfunctional compound as the component (C), there can beexemplified compounds which contain in the molecule two or morefunctional groups selected from the group consisting of amino group,epoxy group, dihydrooxazolyl group, carboxyl group, carboxylic acidanhydride group and hydroxyl group. The molecular weight of thepolyfunctional compound (C) is not critical and the polyfunctionalcompound (C) also includes polymeric compounds.

Specific examples of the compound containing two or more amino groups inthe molecule are given below.

There can be used, for example, aliphatic diamines such as1,6-hexamethylenediamine, trimethylhexamethylenediamine,1,4-diaminobutane, 1,3-diaminopropane, ethylenediamine, polyetherdiamine, etc.; aliphatic diamine carbamates such as hexamethylenediaminecarbamate, ethylenediamine carbamate, etc.; aliphatic polyamines such asdiethylenetriamine, triethylenetetramine, tetraethylenepentamine,pentaethylenehexamine, ethylaminoethylamine, methylaminopropylamine,2-hydroxyethylaminopropylamine, aminoethyl ethanolamine,1,3bis(3-aminopropoxy)-2,2-dimethylpropane, 1,3,6-trisaminomethylhexane,iminobispropylamine, methyliminobispropylamine,bis(hexamethylene)trimaine, etc.; alicyclic polyamines such as menthenediamine, N-aminoethyl piperazine, 1,3-diaminocyclohexane, isophoronediamine, bis(4-amino-3-methylcyclohexyl)methane, etc.; aliphaticpolyamines having an aromatic ring, such as m-xylylenediamine, etc.;aromatic amines such as diaminodiphenyl ether, 4,4-methylenedianiline,diaminodiphenylsulfone, benzidine, 4,4'-bis(o-toluidine),4,4'-thidianiline, dianisidine, methylenebis(o-chloroaniline),bis(3,4-diaminophenyl)sulfone, diaminoditolylsulfone, etc.;silicon-containing polyamines such as1,3-bis(γ-aminopropyl)-1,1,3,3-tetramethyldisiloxane, etc.;aminemodified silicone oil; butadiene-acrylonitrile copolymers whoseterminal functional group is an amine; tertiary amine compounds such asN,N,N',N'-tetramethylhexamethylenediamine,N,N,N',N",N"-pentamethyldiethylenetriamine, etc.; ethylene copolymersconsisting of ethylene units and N,N-dialkylaminoalkyl α,β-unsaturatedcarboxylic acid ester units, such as copolymers of ethylene andN,N-dimethylaminoethyl methacrylate, etc.; and ethylene copolymersconsisting of ethylene and N,N-dialkylaminoalkyl α,β-unsaturatedcarboxylic acid amide units, such as copolymers of ethylene andN,N-dimethylaminopropylacrylamide, etc.

Specific examples of the compound containing two or more epoxy groups inthe molecule are given below.

They are roughly divided into epoxy-groupcontaining olefin copolymersand epoxy compounds.

As the epoxy-group-containing olefin copolymers, there can be usedolefin-glycidyl methacrylate copolymers, olefin-glycidyl acrylatecopolymers, and olefin-glycidyl methacrylate-glycidyl acrylateterpolymers. Specific examples of olefin are ethylene, propylene,butene-1, isobutylene, etc. Of these, ethylene is particularlypreferable. The epoxy-group-containing olefin copolymers may furthercomprise as comonomer an α,β-unsaturated carboxylic acid alkyl esterand/or a carboxylic acid vinyl ester. Specific examples of the alkylesters are alkyl esters of acrylic acid, methacrylic acid and the like.Specific examples of the alkyl esters and the vinyl esters are methylacrylate, ethyl acrylate, nbutyl acrylate, methyl methacrylate, vinylacetate and vinyl propionate. As the epoxy-group-containing olefincopolymers, there can also be exemplified glycidylmethacrylate-modifiedethylene-propylene rubber, ethylene-methyl acrylate-glycidylmethacrylate copolymer rubber, etc.

As to a polymerization method, the epoxy-groupcontaining olefincopolymer may be produced by any of random copolymerization, blockcopolymerization and graft copolymerization. The content of glycidylmethacrylate and/or glycidyl acrylate units in the olefin copolymer ischosen in the range of 1 to 50% by weight. When the content is outsidethis range, the improvement in physical properties of the amide resincomposition is not sufficient in some cases.

As the epoxy compounds, there can be exemplified, for example, glicidylethers of bisphenols such as bisphenol A, resorcinol, hydroquinone,etc., or halides of these bisphenols. Of these, epoxy resins arepreferred.

These epoxy compounds are used alone or as a mixture thereof.

In general, epoxy compounds are used as a blend with a curing agent suchas amine, acid anhydride, polymercaptan, phenol resin or the like. Inthe present invention, no curing agent is usually used but a curingagent may be used so long as the amount of its active hydrogen isequimolar with or smaller than the amount of the epoxy group component.

Specific examples of epoxy resins include bisphenol A epoxy resins,bisphenol F epoxy resins, novolak type epoxy resins, cyclic aliphaticepoxy resins, glycidyl ester resins, glycidylamine resins, hydantointype epoxy resins, triglycidyl isocyanurate, etc.

Specific examples of compound containing two or more hydroxyl groups inthe molecule are trimethylolpropane, pentaerythritol, saponifiedcopolymers of ethylene and vinyl acetate, etc.

Compounds containing two or more dihydrooxazolyl groups in the moleculecan also be used and they include 2,2-(1,3-phenylene)-bis(2-oxazoline),copolymers of styrene and vinyloxazoline, etc.

In the polyamide resin composition according to the present invention,the mixture (I) comprises the polyamide resin as component (A) and themodified olefin polymer as component (B) in amounts of 60 to 20 parts byweight and 40 to 80 parts by weight, respectively, per 100 parts byweight of the whole Mixture (I). When the content of the polyamide resincomponent (A) in Mixture (I) is less than 20 parts by weight, thestiffness and the heat resistance of the resulting polyamide resincomposition are not sufficient. When it exceeds 60 parts by weight, nodesirable effect on the impact resistance of the resulting polyamideresin composition can be obtained. The weight ratio of the component (A)to the component (B) is preferably 60-30/ 40-70, more preferably50-40/50-60.

In the present invention, although the amount added of thepolyfunctional compound as component (C) should be adjusted depending onthe reactivity of functional group of the polyfunctional compound withcarboxyl group, carboxylic acid anhydride group or amino group, it isusually 0.01 to 20 parts by weight, preferably 5 to 15 parts by weight,more preferably 8 to 13 parts by weight, per 100 parts by weight of thetotal amount of the polyamide resin component (A) and the modifiedolefin polymer component (B) [the amount of the whole Mixture (I)].Thus, Mixture (II) can be obtained. When the amount added of thepolyfunctional compound as component (C) in Mixture (II) is less than0.01 part by weight, there is brought about insufficient improvingeffects on mechanical properties such as heat resistance and stiffnessof the polyamide resin composition in some cases. When it exceeds 20parts by weight, the effect of the polyfunctional compound hits theceiling in some cases.

The amount added of the polyamide resin as component (D) in the presentinvention is 50 to 1,000 parts by weight, preferably 100 to 500 parts byweight, more preferably 100 to 200 parts by weight, per 100 parts byweight of Mixture (II). When the amount added is less than 50 parts byweight, the stiffness and the heat resistance of the polyamide resincomposition are not sufficient. When it exceeds 1,000 parts by weight,no desirable effect on the impact resistance of the polyamide resincomposition can be obtained.

The process for producing a polyamide resin composition of the presentinvention comprises meltkneading the starting materials in molten state.A method for blending the starting materials in said process comprisesmelt-kneading the polyamide resin component (A) with the modified olefinpolymer component (B) to obtain partially crosslinked Mixture (I),adding thereto the polyfunctional compound (C), melt-kneading theresulting mixture to carry out partial crosslinking reaction, therebypreparing Mixture (II), then adding thereto the polyamide resin ascomponent (D), and meltkneading the resulting mixture.

The polyamide resin composition of the present invention has very goodbalance in various physical properties of molded product, for example,mechanical properties such as impact resistance and the like and thermalproperties. In particular, the product possesses an increased stiffnessand melt index and hence an improved processability by virtue of thesubsequent addition of the polyamide resin as component (D) followed bymelt-kneading.

The reason why the melt-kneading by the above specified blending methodbrings about a marked physicalproperties-improving effect is assumedthat a microdispersed state of a polymer having satisfactory physicalproperties is formed by moderate crosslinking action.

When the polyamide resin (A) and the modified olefin polymer (B) aremelt-kneaded together, the modified olefin polymer becomes a matrixphase at the beginning of melt-kneading because its melting point islower than that of the polyamide resin. When the melt-kneaing is furthercontinued and the polyadmide resin as component (D) is added, the volumeof the polyamide resin components becomes larger than that of themodified olefin polymer, so that the polyamide resins undergo phaseinversion to a matrix phase. Therefore, in the present invention, thephase inversion is stopped en route by adding a partial-crosslinkingagent consisting of a polyfunctional compound.

As a result, there is formed a multi-dispersed state in which a modifiedolefin polymer phase containing polyamide resin particles is dispersedin the polyamide resins. This dispersed state is similar to that formedin the case of impact-resistant polystyrene and is considered to givethe most desirable physical properties.

The shape and size of the olefin polymer phase are not essentiallycritical. In this point, the present invention can be said to be a noveltechnical idea which is clearly distinguishable from the ideas of theprior art (disclosed in JP-B-55-44108, JP-A-61163960, etc.) that whenthe particle size of rubbery dispersed phase of an olefin polymercomponent or the like is as very small as, for example, less than 1micron, its improving effect is excellent to a certain degree.

In general, the improvement of resistance to thermal deformation tendsto result in an increased stiffness and a lowered impact resistance. Bycontrast, in the case of the composition obtained by the process of thepresent invention, the heat resistance and the impact resistance can beimproved with good balance between them without deterioration of otherphysical properties. Such the improvement cannot be expected noranticipated from the prior art.

For the melt-kneading in the process of this invention, there can beused a conventional kneading apparatus, for example, various extruderssuch as single- or twin-screw extruders, Banbury mixer, roll mill, andother various kneaders.

The polyfunctional compound component (C) of the present invention isadded and melt-kneaded, for example, in the following manners. Amelt-kneaded mixture of the polyamide component (A) and the modifiedolefin polymer component (B) is prepared in the form of particles withan extruder, and then the polyfunctional compound component (C) is addedthereto, followed by melt-kneading the resulting mixture with anextruder. Thus, the polyamide resin composition of this invention can beproduced. Preferably, using an extruder equipped with a side-feeddevice, a meltkneaded mixture of the polyamide resin component (A) andthe modified olefin polymer component (B) is prepared in the anterior(front) part of the extruder, and the polyfunctional compound (C) insolid or molten state is added thereto in the posterior (back) part ofthe extruder by means of the side-feed device, followed by melt-kneadingthe resulting mixture, whereby the polyamide resin composition isproduced.

It is also preferable to prepare a master batch by melt-kneading thepolyfunctional compound component (C) with a resin inert theretopreviously, add an adequate amount of the batch at the time ofproduction, and melt-knead the resulting mixture.

The polyamide resin as component (D) of the present invention is addedand melt-kneaded, for example, in the following manners. Mixture (II)consisting of the polyfunctional compound (C) and Mixture (I) obtainedby melt-kneading the polyamide resin component (A) with the modifiedolefin polymer component (B) is prepared in the form of particles, forexample, with an extruder, and then the polyamide resin as component (D)is added thereto, followed by melt-kneading the resulting mixture withan extruder. Thus, the polyamide resin composition of this invention canbe produced. Preferably, said polyamide resin composition can beproduced using an extruder equipped with a sidefeed device. In detail,it is preferable to produce said composition by preparing Mixture (I) atfirst by melt-kneading the polyamide resin component (A) with themodified olefin polymer component (B) in the anterior (front) part ofthe extruder, then preparing Mixture (II) by adding the polyfunctionalcompound (C) in the middle (intermediate) part of the extruder throughthe side-feed device, and adding the polyamide resin as component (D) inmolten or solid state in the posterior (back) part of the extruderthrough the side-feed device, and finally by melt-kneading the resultingmixture.

The object of the present invention can be achieved also by a simplemelt-kneading with an injection molding machine. In detail, a moldedproduct having satisfactory physical properties can be obtained at astroke, for example, by dry blending pellets obtained by granulation ofMixture (II) with the polyamide resin as component (D), andinjection-molding the resulting blend directly.

In the process of the present invention, before melt-kneading thecomponents, the components have preferably made into a uniform mixtureof powder or pellet with an apparatus such as tumbler or Henschel mixer.However, there can be optionally employed a method in which the mixingis omitted and predetermined amounts of the components are individuallyfed to a meltkneading apparatus.

In the resin composition obtained according to the present invention maycontain other constituents, for example, additives such as pigments,dyes, reinforcing agents, fillers, heat stabilizers, antioxidants,weathering stabilizers, nucleating agents, lubricants, antistaticagents, flame retardants, plasticizers and the like, or other polymers.

Particularly adding reinforcing agents or fillers, such as glass fiberssuffered from various surface treatments, carbon fiber, talc, calciumcarbonate, magnesium hydroxide, etc. to the resin composition obtainedaccording to the process of the present invention gives a very usefulmaterial having a high stiffness and a high impact strength.

The resin composition obtained according to the present invention ismolded by various molding methods such as injection molding, extrusionmolding, etc.

The following examples serves to give specific illustration of thepractice of the present invention but they are not intended in any wayto limit the scope of the present invention. In the examples, theflexural modulus (sample thickness: 3.2 mm, measuring temperature: 23°C.) was measured according to JIS K7203 and the Izod impact strength(sample thickness: 3.2 mm, measuring temperatures: 23° C. and -40° C.;V-notched) according to JIS K7110. In Tables 1 and 2, "NB" indicatesthat the Izod impact strength was 50 kg.cm/cm or more and that a testpiece was not broken.

The thermal deformation temperature (sample thickness: 3.2 mm, flexurestress: 4.6 kg f/cm²) and the melt index (Ml, 2160 g) were measuredaccording to JIS K7207 and JIS K6760, respectively.

The amount of maleic anhydride added in the modified olefin polymer wasdetermined by dissolving a small amount of an extruded sample in xylene,adding anhydrous acetone to cause precipitation, redissolving the thuspurified sample in xylene, and titrating the resulting solution with asolution of KOH in ethanol with heating (85° C.) by usingphenolphthalein as an indicator.

In the Examples and Comparative Examples, the following polyamideresins, modified olefin polymers and polyfunctional compounds were used.

(A) and (D): Polyamide resins

(1) Polyamide 66, Maranyl® A125 (polyhexamethylene adipamide mfd. byUnitika, Ltd.)

(2) Polyamide 6, A1030BRL (poly-ε-caprolactam mfd. by Unitika, Ltd.)

(B): Modified olefin polymer

(1) Modified polymer (1)

A modified polymer (1) was obtained by mixing 100 parts by weight of anethylene propylene copolymer rubber [glass transition temperature: -58°C., propylene unit content: 22% by weight, MI (230° C.): 1.9 g/10min]with 2 parts by weight of maleic anhydride, 0.08 part by weight of1,3-bis(t-butylperoxyisopropyl)benzene and 2 parts by weight of styrene,charging the resulting mixture into a twin screw extruder whose die hasan inner diameter of 44 mm under a nitrogen atmosphere, andmelt-kneading the same at a resin temperature of 250° C. The modifiedpolymer (1) obtained had an amount of maleic anhydride added of 1.6% byweight and an MI (230° C.) of 0.3 g/10 min.

(2) Modified polymer (2)

A modified polymer (2) was obtained by mixing 100 parts by weight of apropylene-ethylene block copolymer [glass transition temperature: -43°C., ethylene unit content: 12.5% by weight, MI (230° C.): 3 g/10 min]with 1 part by weight of maleic anhydride, 1 part by weight of1,3-bis(t-butylperoxyisopropyl)benzene, 0.5 part by weight of styreneand 0.1 part by weight of an antioxidant Irganox® 1010, charging theresulting mixture into a twin screw extruder whose die has an innerdiameter of 44 mm under a nitrogen atmosphere, and melt-kneading thesame at a resin temperature of 230° C. The modified polymer (2) had anamount of maleic anhydride added of 0.3% by weight and an MI (230° C.)of 4.5 g/10 min.

(3) Modified polymer (3)

A modified polymer (3) was obtained by mixing 100 parts by weight of anethylene-methyl methacrylate copolymer [glass transition temperature:-34° C., methyl methacrylate unit content: 38% by weight, MI (190° C.):7 g/10 min] with 1 part by weight of maleic anhydride and 0.1 part byweight of t-butyl peroxylaulate, charging the resulting mixture into atwin screw extruder whose die has an inner diameter of 30 mm under anitrogen atmosphere, and melt-kneading the same at a resin temperatureof 200° C. The modified polymer (3) obtained had an amount of maleicanhydride added of 0.3% by weight and an MI (190° C.) of 4 g/10 min.(C): Polyfunctional compound

(1) MB-1

A master batch prepared by melt-kneading 5 parts by weight ofhexamethylenediamine carbamate with 95 parts by weight of Grilon® CF6S(a copolymerization polyamide resin mfd. by EMS-CHEMIE AG) at 150° C.with a single screw vented extruder whose die has an inner diameter of30 mm.

(2) Bondfast® E (mfd. by Sumitomo Chemical Co.) Ethylene-glycidylmethacryl copolymer [glycidyl methacrylate unit content: 12% by weight,MI (190° C.): 3 g/10 min]

(3) E-DAM copolymer

Ethylene-dimethylaminoethyl methacrylate copolymer [dimethylaminoethylmethacrylate unit content: 28% by weight, MI (190° C.): 100 g/10 min]

(4) E-VA sapnified product

Saponified product of an ethylene-vinyl acetate copolymer [vinyl acetateunit content: 43% by weight, MI (190° C.): 70 g/10 min] [saponificationrate: 99%, MI (190° C.): 35 g/10 min]

(5) MB-2

A master batch prepared by melt-kneading 5 parts by weight of2,2'-(1,3-phenylene)-bis(2-oxazoline) with 95 parts by weight of Acryft®WH303 at 200° C. with a single screw vented extruder whose die has aninner diameter of 30 mm.

Acryft® WH303: ethylene-methyl methacrylate copolymer (mfd. by SumitomoChemical Co.) [methyl methacrylate unit content: 18% by weight, MI (190°C.): 7 g/10 min

Examples 1 to 9

Mixture (I) was obtained by melt-kneading together each component (A)and each component (B) listed in Table 1 with a single screw ventedextruder whose die has an inner diameter of 30 mm at a prescribedtemperature (270° C. for Polyamide 66 and 240° C. for Polyamide 6).

Mixture (II) was obtained by mixing Mixture (I) with each component (C)listed in Table 1, and melt-kneading the resulting mixture by the samesingle screw vented extruder as above at a prescribed temperature (270°C. for Polyamide 66 and 240° C. for Polyamide 6).

With a twin screw vented extruder whose die has an inner diameter of 44mm equipped with a side-feed device, a polyamide resin composition wasobtained by feeding Mixture (II) in a metering manner through aside-feed device provided in the middle of the extruder barrel, whilemelt-kneading each component (D) listed in Table 1 with the fed mixtureat a prescribed temperature (270° C. for polyamide 66 and 240° C. forpolyamide 6).

Table 1 shows the melt index of the resin composition obtained.

Each resin composition was dried at 80° C. for 12 hours and then madeinto test pieces for measuring physical properties, with a 10-ounceinjection molding machine (Toshiba Model IS-150-V) at a die temperatureof 70° C at a prescribed temperature (290° C. for polyamide 66 and 260°C. for polyamide 6).

Table 1 shows the flexural modulus, Izod impact strength and thermaldeformation temperature of the test pieces thus obtained.

Comparative Examples 1 and 6

A mixture was obtained by melt-molding together each component (A) andthe component (B) listed in Table 2 with a single screw vented extruderwhose die has an inner diameter of 30 mm at a prescribed temperature(270° C. for polyamide 66 and 240° C. for polyamide 6).

The mixture was mixed with the component (C) listed in Table 2 and theresulting mixture was melt-kneaded with a twin screw vented extruderwhose die has an inner diameter of 44 mm at a prescribed temperature(270° C. for polyamide 66 and 240° C. for polyamide 6) to obtain a resincomposition.

Table 2 shows the results of evaluation of each of the resincompositions obtained in the same manner as in Example 1. Both of theseresin compositions are inferior to those obtained in Examples 1 and 8 inflow properties, stiffness and thermal deformation temperature.

Comparative Example 2

A resin composition was obtained by mixing and melt-kneading thecomponents (A), (B) and (C) listed in Table 2, in one lot at 240° C.with a twin screw vented extruder whose die has an inner diameter of 44mm.

Table 2 shows the results of evaluation of the resin composition in thesame manner as in Example 1. This resin composition is inferior to thatof Example 1 in Izod impact strength.

Comparative Example 3

A resin composition was obtained by melt-kneading together thecomponents (A) and (B) listed in Table 2 with a single screw ventedextruder whose die has an inner diameter of 30 mm.

Table 2 shows the results of evaluation of the resin composition in thesame manner as in Example 1. This resin composition is inferior to thatof Example 1 in flow properties, stiffness and thermal deformationtemperature.

Comparative Example 4

A mixture was obtained by melt-kneading the components (A) and (C)listed in Table 2 at 240° C. with a single screw vented extruder whosedie has an inner diameter of 30 mm.

With a twin screw vented extruder whose die has an inner diameter of 44mm equipped with a side-feed device, a resin composition was obtained byfeeding the aforesaid mixture in a metering manner through the side-feeddevice provided in the middle of the extruder barrel, whilemelt-kneading the second component listed in Table 2 with the fedmixture at 240° C.

Table 2 shows the results of evaluation of the resin composition in thesame manner as in Example 1. This resin composition is inferior to thatof Example 2 in Izod impact strength.

Comparative Examples 5 and 7

In the same manner as in Example 1, Polyamide 6 or Polyamide 66 wasmolded and the physical properties of the molded products thus obtainedwere evaluated. Table 2 show the results obtained.

                                      TABLE 1                                     __________________________________________________________________________    Polyamide resin composition                                                   Mixture (II)                                                                  Mixture (I)                                                                         Component (A)                                                                 (parts by                                                                             Component (B)                                                                            Component (C)                                                                           Component (D)                                    weight) (parts by weight)                                                                        (parts by weight)                                                                       (parts by weight)                          __________________________________________________________________________    Example 1                                                                           Polyamide 6                                                                           Modified polymer (1)                                                                     MB-1      Polyamide 6                                      45      45         10        125                                        Example 2                                                                           Polyamide 6                                                                           Modified polymer (1)                                                                     Bondfast ® E                                                                        Polyamide 6                                      45      45         10        125                                        Example 3                                                                           Polyamide 6                                                                           Modified polymer (1)                                                                     Copolymer E-DAM                                                                         Polyamide 6                                      45      45         10        125                                        Example 4                                                                           Polyamide 6                                                                           Modified polymer (1)                                                                     E-VA Saponified                                                                         Polyamide 6                                      45      45         product 10                                                                              125                                        Example 5                                                                           Polyamide 6                                                                           Modified polymer (1)                                                                     MB-2      Polyamide 6                                      45      45         10        125                                        Example 6                                                                           Polyamide 6                                                                           Modified polymer (2)                                                                     MB-1      Polyamide 6                                      45      45         10        125                                        Example 7                                                                           Polyamide 6                                                                           Modified polymer (3)                                                                     MB-1      Polyamide 6                                      45      45         10        125                                        Example 8                                                                           Polyamide 66                                                                          Modified polymer (1)                                                                     MB-1      Polyamide 66                                     40      50         10        200                                        Example 9                                                                           Polyamide 66                                                                          Modified polymer (1)                                                                     Bondfast  ® E                                                                       Polyamide 66                                     40      50         10        200                                        __________________________________________________________________________                  Physical properties of polyamide resin composition                                                   Thermal                                                              Izod impact                                                                            deformation                                                     Flexural                                                                           strength temp.                                                  MI2160 g, 230° C.                                                               modulas                                                                            (kg · cm/cm)                                                                  (4.6 kg/cm.sup.2)                                      (g/10 min)                                                                             (kg/cm.sup.2)                                                                      23° C.                                                                     -40° C.                                                                     (° C.)                            __________________________________________________________________________            Example 1                                                                           15       17500                                                                              NB  14   165                                              Example 2                                                                           11       18000                                                                              NB  14   160                                              Example 3                                                                           10       17100                                                                              NB  13   159                                              Example 4                                                                            9       17000                                                                              NB  11   161                                              Example 5                                                                           12       17300                                                                              NB  11   160                                              Example 6                                                                           25       22100                                                                              36  10   162                                              Example 7                                                                            9       17000                                                                              NB  11   163                                              Example 8                                                                           13       17800                                                                              NB  17   200                                              Example 9                                                                           10       18500                                                                              NB  18   197                                      __________________________________________________________________________

                                      TABLE 2                                     __________________________________________________________________________           Polyamide resin composition                                                   Mixture (II)                                                                  Mixture (I)                                                                   Component (A)                                                                 (parts by                                                                             Component (B)                                                                            Component (C)                                                                          Component (D)                                     weight) (parts by weight)                                                                        (parts by weight)                                                                      (parts by weight)                          __________________________________________________________________________    Comparative                                                                          Polyamide 6                                                                           Modified polymer (1)                                                                     MB-1     --                                         Example 1                                                                            170     45         10                                                  Comparative                                                                          Polyamide 6                                                                           Modified polymer (1)                                                                     MB-1     --                                         Example 2                                                                            170     45         10                                                  Comparative                                                                          Polyamide 6                                                                           Modified polymer (1)                                                                     --       --                                         Example 3                                                                            180     45                                                             Comparative                                                                          Polyamide 6                                                                           --         Bondfast ® E                                                                       Polyamide 6                                Example 4                                                                             45                55       125                                        Comparative                                                                          --      --         --       Polyamide 6                                Example 5                                                                     Comparative                                                                          Polyamide 66                                                                          Modified polymer (1)                                                                     MB-1     --                                         Example 6                                                                            240     50         10                                                  Comparative                                                                          --      --         --       Polyamide 66                               Example 7                                                                     __________________________________________________________________________                  Physical properties of polyamide resin composition                                                   Thermal                                                              Izod impact                                                                            deformation                                                     Flexural                                                                           strength temp.                                                  MI2160 g, 230° C.                                                               modulas                                                                            (kg · cm/cm)                                                                  (4.6 kg/cm.sup.2)                                      (g/10 min)                                                                             (kg/cm.sup. 2)                                                                     23° C.                                                                     -40° C.                                                                     (°C.)                             __________________________________________________________________________           Comparative                                                                          3        16800                                                                              NB  13   152                                             Example 1                                                                     Comparative                                                                          4        16100                                                                              7   5    170                                             Example 2                                                                     Comparative                                                                          4        16400                                                                              NB  13   125                                             Example 3                                                                     Comparative                                                                          20       18100                                                                              20  7    167                                             Example 4                                                                     Comparative                                                                          34       26300                                                                              2   1    178                                             Example 5                                                                     Comparative                                                                          3        16700                                                                              NB  17   185                                             Example 6                                                                     Comparative                                                                          68       29000                                                                              4   3    231                                             Example 7                                                              __________________________________________________________________________

As described above, according to the present invention, there isprovided a process for producing a polyamide resin composition which ismarkedly advantageous in having a very good balance in variousproperties of molded product (for example, mechanical properties such asimpact resistance and the like), thermal properties and a goodappearance.

In particular, it is a surprising finding unanticipated from the priorart that conducting the melt-kneading by a specific two-step blendingimproves the resistance to thermal deformation of the product without areduction of the impact resistance.

The polyamide resin composition provided by the present inventionexhibits a good flow properties and can easily be processed into amolded product, a film, a sheet or the like by a molding method used forconventional polyamide resin compositions, for examples, injectionmolding, extrusion molding or the like. Moreover, the molded product hasa very good balance in physical properties such as impact resistance,stiffness, heat resistance, etc., and a uniform and smooth appearance.

What is claimed is:
 1. A process for producing an impactresistantpolyamide resin which comprises(1) preparing Mixture (I) bymelt-kneading (A) 60 to 20 parts by weight of a polyamide resin with (B)40 to 80 parts by weight of at least one modified olefin polymer havinga glass transition temperature of -10° C. or lower selected from thegroup consisting of copolymer rubbers of ethylene and an α-olefin having3 or more carbon atoms which rubbers have 0.01 to 9% by weight of anunsaturated dicarboxylic acid anhydride added theretoethylene-ethylenically unsaturated ester copolymers having 0.01 to 9% byweight of an unsaturated dicarboxylic acid anhydride added thereto, (2)preparing Mixture (II) by melt-kneading 100 parts by weight of Mixture(I) with (C) 0.01 to 20 parts by weight of a polyfunctional compoundselected from the group consisting of aliphatic diamine carbamates,aliphatic polyamines, alicyclic polyamines and aromatic amines, and (3)melt-kneading 100 parts by weight of Mixture (II) with (D) 50 to 1,000parts by weight of a polyamide resin.
 2. A process for producing animpact-resistant polyamide resin composition which comprises(1)preparing Mixture (I) by melt-kneading (A) 60 to 20 parts by weight of apolyamide resin with (B) 40 to 80 parts by weight of a modified olefinpolymer obtained by melt-kneading 100 parts by weight of at least oneolefin polymer having a glass transition temperature of -10° C. or lowerselected from the group consisting of copolymer rubbers of ethylene andan α-olefin having 3 or more carbon atoms and ethylene-ethylenicallyunsaturated ester copolymers, with 0.1 to 10 parts by weight of anunsaturated dicarboxylic acid anhydride, (2) preparing Mixture (II) bymelt-kneading 100 parts by weight of Mixture (I) with (C) 0.01 to 20parts by weight of a polyfunctional compound selected from the groupconsisting of aliphatic diamine carbamates, aliphatic polyamines,alicyclic polyamines and aromatic amines, and (3) melt-kneading 100parts by weight of Mixture (II) with (D) 50 to 1,000 parts by weight ofa polyamide resin.
 3. A process according to claim 2, wherein themodified olefin polymer (B) is obtained by melt-kneading 100 parts byweight of at least one olefin polymer having a glass transitiontemperature of -10° C. or lower selected from the group consisting ofcopolymer rubbers of ethylene and an α-olefin having 3 or more carbonatoms and ethylene-ethylenically unsaturated ester copolymers, with 0.1to 10 parts by weight of an unsaturated dicarboxylic acid anhydride and0.01 to 50 parts by weight of an aromatic vinyl monomer.
 4. A processaccording to claim 2, wherein the unsaturated dicarboxylic acidanhydride added to the modified olefin polymer (B) is maleic anhydride.5. A process according to claim 1, wherein the copolymer rubber is anethylene-propylene copolymer.
 6. A process according to claim 2, whereinthe copolymer rubber is an ethylene-propylene copolymer.
 7. A processaccording to claim 1, wherein the polyfunctional compound ishexamethylenediamine carbamate.
 8. A process according to claim 2,wherein the polyfunctional compound is hexamethylenediamine carbamate.